This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Crystallographic studies of a series of human and bacterial proteins are proposed, with the unifying theme that each protein plays a role in human disease. First, the structure of the Pseudomonas protein PilY1 will be pursued using a combination of MAD and SAD methodologies. This protein is the adhesion that attaches the infectious Psuedomonas bacterium to the lung epithelia, leading to lethal colonizations in patients with cystic fibrosis (CF). Second, crystal structures of the human drug metabolism protein carboxylesterase 1 (hCE1) will be determined in complexes with nerve agents (e.g., sarin, soman) and nerve agent analogues. Third, crystal structures of human nuclear receptors will be determined. For example, structures of the nuclear xenobiotic receptor PXR will be determined in complexes with various drugs and antagonists;PXR is the central drug receptor in humans and controls the expression of the primary drug metabolism pathways in liver and other tissues. In the cases of hCE1 and nuclear receptors, synchrotron radiation is required because the crystals we have diffract to